Permanent magnet speed governors realize speed regulation through the magnetic coupling of permanent magnet and realize the flexible (magnetic) connection of motors and loads, without any harmonic waves affecting power grid, with high reliability, and they can work in various severe environments such as high temperature, low temperature, humid environment, dirty environment, inflammable and explosive environment, unsteady voltage and thunder, greatly reducing mechanical vibration; they are widely used in power, iron and steel, metallurgy, petrochemical, paper-making, municipal engineering, ship, irrigation and mining industries. However, the existing commonly-used permanent magnet speed governors realize speed regulation through the adjustment of air gap, and the power consumption of magnetic circuit regulator is large, and there are shortcomings such as poor torque transmission capability, high difficulty in assembling and a waste of lots of rare earth resources.